The Office of Personnel Management may be little known to the general public, but perhaps no agency matters more to some 2.7 million federal civil service employees and U.S. Postal Service workers. So, they might want to keep an ear out Tuesday, when a Senate panel has scheduled a hearing on the nomination of Katherine Archuleta to become the next OPM director. The job has been vacant since April when John Berry (since selected for the Australia ambassadorship) resigned just before his four-year term was up. Filling in is OPM General Counsel Elaine Kaplan, but she’s been nominated for a…